INFESTATIONS rise as more farmers use pour-on treatments, writes BRIAN CLANCY
Greg Richards has a lousy job, literally.
His business, Dipping Dynamics, involves three mobile dipping plants that travel throughout Victoria, South Australia and NSW to treat up to a million sheep a year in the never-ending battle against lice.
In fact, the former animal health chemical salesmen turned dipping contractor sees no end in the fight against sheep lice.
Two years ago, Greg won the right to continue dipping with diazinon which, despite its effectiveness in killing lice, has been banned from all but a few limited on-farm uses because of its dangers to humans.
Greg conducted some very extensive and expensive trials to prove that his caged dipping system, which he designed and built himself, could be operated safely with sheep, within the environment but more importantly to the operator.
Under licensing arrangements with the Australian Pesticides and Veterinary Medicines Authority, Dipping Dynamics is the only company or operator allowed to dip sheep using diazinon. Others who do so risk prosecution.
But, as Greg said, removing diazinon from on-farm dips and jetting systems was one of the reasons for a rise in lice infestations.
Diazinon has, for decades, been the only chemical not to develop any known insect resistance.
State department estimates suggest that 40-70 per cent of the nation's flocks were now infested with lice costing $120 million in lost production and treatment.
Greg blamed the increased level of infestations on a move to the pour-on or backliner treatments some of which were already developing resistances.
He said proper control of lice needed a total farm plan, including proper fencing to prevent straying sheep.
"In the old days people breeding their own Merinos could keep the problem under control.
"But today's Merino is generally bigger and producing a denser fleece which made it all that much harder to treat for lice."
Greg said the move into prime lambs had also increased the risk of a lice infestation and cross infestations between flocks.
"Merino sheep normally respected a fence, whereas crossbreds see fences as a challenge," Greg said.
"Even when you buy a ram you have to be careful you don't re-introduce lice.
"Just because you buy a ram from a reputable stud is no guarantee."
He said infestations could be introduced on to the farm in many ways and not just from straying sheep.
"If you are going to dip, dip all sheep including pets and killers.
"And those breeds which shed their wool can carry a lice infestation like any woolly sheep."
Greg is adamant the only foolproof control for lice is a "wettable" treatment in a dipping operation rather than by jetting.
Apart from the banned diazinon, Greg said there were two other wettable treatments - Elanco's Extinosad and Coopers' Assassin - both which could be effectively used in plunge dips.
Both are considerably more expensive than diazinon, although the Extinosad, which is derived from a soil bacteria, doesn't have the meat or wool withholding times which apply to diazinon or the organophosphate Assassin.
To be really effective Greg recommended that sheep be treated with a wettable no longer than six weeks off shears and that the sheep be immersed or swim for at least 40 seconds in dipping operation, which should also include two "head dunks".
Which is the reason he is not a fan of the plunge dips with a short race because the sheep are not immersed for long enough.
